Gas-Surface Dynamics and Profile Evolution during Etching of Silicon

Abstract

Scattering of energetic F atoms on a fluorinated Si surface is studied by molecular beam methods. The energy transfer closely follows hard-sphere collision kinematics. Energy and angular distributions of unreacted F atoms suggest significant multiple-bounce scattering in addition to single-bounce scattering and trapping desorption. An empirical model of the atom-surface interaction dynamics is used in a Monte Carlo simulation of topography evolution during neutral beam etching of Si. Model predictions of profile phenomena are validated by experiments. [S0031-9007(96)

On the origin of the notching effect during etching in uniform high density plasmas

“…We hypothesize that such an angle exists for the Cl ϩ etching of Si, based on our results for fluorine scattering at fluorosilyl layers. 10 However, the notch characteristics were found to be insensitive to the value of cr ͑between 30°and 60°͒ as a result of the nature of scattering on the chlorinated poly-Si surface: beyond the initial stages of notching and excluding the apex of the notch, most of the ions impinge at large incident angles, typically у50°, where forward scattering is already significant. For the results presented here, we set cr ϭ45°.…”

“…Direct inelastic scattering was found to be uniquely responsible for microtrenching in hyperthermal neutral beam etching. 10 A notch is indeed reminiscent of a sharp microtrench ͑with a 90°clockwise rotation͒ and both phenomena have a common origin in the forward scattering of energetic particles, albeit the contribution to notching is smaller. Thus, no new mechanism is required to explain notching.…”

“…Scattering on the photoresist surfaces is not important for notching. Among the different modes of scattering, 10 only direct inelastic ͑or single-bounce͒ scattering is important for notching as a result of the large translational energy of the emerging particles. In spite of the large numbers of ions that undergo multiple-bounce scattering and trapping desorption, these ions do not have large enough energy to induce physical or chemical sputtering in a subsequent collision event and are therefore neglected.…”

“…We employ a simple model of sputtering and scattering, based on previous simulations of profile evolution during neutral beam etching. 10 When a hyperthermal Cl ϩ impinges on the SiCl x salvage layer, it will etch with a yield Y that depends on the incident energy E i and angle i , as described by the simple formula …”

Scattering of Nitrogen Atoms off Ag(111) Surfaces: A Theoretical Study

“…This kind of decomposition of the effusive beam according to the initial energy range of N atoms had already been performed in previous works for the experimental scattering of F atoms on a fluorinated Si surface where two distinct scattering processes had also been suggested: 58,59 (i) multiple bounce/indirect scattering giving a cosine distribution that corresponds to our lower E T i and (ii) single bounce/direct scattering resulting in a broad specular distribution that corresponds to our higher E T i . However, note that, in our case, we can not discriminate between the two scattering processes by using the number of rebounds, since it remains quite low at any E T i .…”